System and method for sectorized transmission in a wireless network

ABSTRACT

The hidden node problem can be avoided by scheduling stations in different sectors to perform transmissions during different time periods. Sectorized scheduling can be communicated to stations through transmission of beamformed beacon signals at the beginning of respective time periods. For instance, a first beamformed beacon signal may be transmitted to stations in a first sector at the beginning of a first time period, while a second beamformed beacon signal may be transmitted to stations in a second sector at the beginning of a second time period.

This application claims the benefit of U.S. Provisional Application No.61/606,830 filed on Mar. 5, 2012, entitled “System and Method forSectorized Transmission in a Wireless Network,” which is incorporatedherein by reference as if reproduced in its entirety.

TECHNICAL FIELD

The present invention relates to a system and method for wirelesscommunications, and, in particular embodiments, to systems and methodsfor sectorized transmission in a wireless network.

BACKGROUND

In wireless fidelity (Wi-Fi) networks, mobile stations (STAs) accessingthe uplink communications channel employ a carrier sense multiple accesswith collision avoidance (CSMA/CA) technique to avoid collisions withother STAs accessing the uplink channel. More specifically, a STA willverify that the uplink channel is idle before performing an uplinktransmission, which tends to reduce collisions, where two STAs aretransmitting at the same time. This CSMA/CA technique works relativelywell when STAs utilize moderate to high transmit power in mid-to-smallsized wireless local area networks (WLANs), e.g., radius less than fiftymeters, as STAs are typically able detect one another's uplinktransmissions, and thereby avoid transmissions that will result in acollision.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved, by embodiments of thisdisclosure which describe systems and methods for sectorizedtransmission in a wireless network.

In accordance with an embodiment, a method for scheduling in a wirelessnetwork is provided. In this example, the method includes schedulingtransmissions for multiple groups of mobile stations (STAs) in amulti-sector coverage area. Groups of STAs positioned in differentsectors of the multi-sector coverage area are scheduled to performtransmissions during different time periods. The method further includestransmitting a first signal to a first group of STAs positioned in afirst sector of the multi-sector coverage area. The first signalindicates that the first group of STAs is scheduled to performtransmissions during a first time period. The first time period isdifferent from a second time period during which a second group of STAsis scheduled to perform transmissions. An apparatus configured toperform this method is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a diagram of a wireless network for communicatingdata;

FIG. 2 illustrates a diagram of a hidden node problem in acommunications network;

FIG. 3 illustrates a diagram of an embodiment network configured forsectorized transmissions;

FIG. 4 illustrates a flowchart of an embodiment method for schedulingtransmissions;

FIG. 5 illustrates a flowchart of an embodiment method for performingtransmissions;

FIG. 6 illustrates a diagram of another embodiment network configuredfor sectorized transmissions;

FIG. 7 illustrates a diagram of a channel;

FIG. 8 illustrates a diagram of an embodiment for sectorized channelaccess;

FIG. 9 illustrates a diagram of another embodiment for sectorizedchannel access;

FIG. 10 illustrates a diagram of yet another embodiment for sectorizedchannel access.

FIG. 11 illustrates a diagram of an embodiment for sectorized channelaccess using an omni-directional beacon;

FIG. 12 illustrates a diagram of another embodiment for sectorizedchannel access using an omni-directional beacon;

FIG. 13 is a block diagram illustrating a computing platform; and

FIG. 14 illustrates a block diagram of an embodiment communicationsdevice.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of embodiments of this disclosure are discussed indetail below. It should be appreciated, however, that the conceptsdisclosed herein can be embodied in a wide variety of specific contexts,and that the specific embodiments discussed herein are merelyillustrative and do not serve to limit the scope of the claims. Further,it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of this disclosure as defined by the appended claims.

The above discussed CSMA/CA techniques may be less effective in largerWLANs (e.g., radius exceeding fifty meters) and/or when STAs typicallyuse low transmit power, as STAs may often be unable to detect oneanother's transmissions. More specifically, a hidden node problem (asdiscussed in greater detail below in reference to FIG. 2) occurs whentwo or more STAs located outside of one another's carrier range performsimultaneous transmissions to a centrally located base station, therebyresulting in a collision. The hidden node problem is a significantconcern for next generation Wi-Fi networks, some of which are likely toinclude large cells as well as high numbers of low transmit power STAs.For instance, Institute of Electrical and Electronics (IEEE) 802.11ah isa next-generation Wi-Fi standard for smart sensors and metering, andwill likely be implemented in WLANs having a radius of up to onekilometer and housing high numbers of low transmit-power sensor devices.Accordingly, mechanisms for addressing the hidden node problem in Wi-Finetworks is desired.

Aspects of this disclosure avoid the hidden node problem by schedulingtransmissions in different sectors during different time periods. Morespecifically, STAs in the same sector are more likely to be within oneanother transmission range, and are therefore more likely to detect oneanother's carrier transmissions. As a result, scheduling STAs indifferent sectors to transmit during different time periods maysignificantly reduce collisions resulting from the hidden node problem.Scheduling of sectors is communicated to sectors via transmission ofbeamformed beacon signals at the beginning of respective time periods.For instance, a first beamformed beacon signal may be transmitted toSTAs in a first sector at the beginning of a first time period, while asecond beamformed beacon signal may be transmitted to STAs in a secondsector at the beginning of a second time period.

FIG. 1 illustrates a network 100 for communicating data. The network 100comprises an access point (AP) 110 having a coverage area 112, aplurality of STAs 120, and a backhaul network 130. The AP 110 maycomprise any component capable of providing wireless access by, interalia, establishing uplink (dashed line) and/or downlink (dotted line)connections with the STAs 120. The AP 110 can also be referred as a basestation, an enhanced base station (eNB), a femtocell, a controller andother wirelessly enabled devices. The STAs 120 may comprise anycomponent capable of establishing a wireless connection with the AP 110.The STA 120 can be referred as a user equipment, a mobile station, orany other wireless devices. The backhaul network 130 may be anycomponent or collection of components that allow data to be exchangedbetween the AP 110 and a remote end (not shown). In some embodiments,the network 100 may comprise various other wireless devices, such asrelays, femtocells, etc.

A hidden node problem may occur when transmitters employing CSMA/CAtransmission techniques are outside of one another's transmission range.FIG. 2 illustrates a hidden node problem in a communications network200. As shown, the network 200 includes a base station 210 having aserving cell 202, a transmitter 221 having a transmission range 232, anda transmitter 222 having a transmission range 232. As shown, thetransmitters 221-222 are positioned within the cell 202, and thereforemay attempt to perform transmissions to the base station 210 inaccordance with a CSMA/CA transmission technique. However, since the STA221 is outside the transmission range 232 of the STA 222, the STA 221may be unable to detect carrier signals of the STA 222. Likewise,because the STA 222 is outside the transmission range 231 of the STA221, the STA 222 may be unable to detect carrier signals of the STA 221.As such, the STAs 221-222 may perform sequential (or overlapping)transmissions that collide or are otherwise decodable by the basestation 210. Such a situation may often be referred to as the hiddennode problem.

Aspects of this disclosure avoid the hidden node problem by schedulingtransmissions sector by sector. While the transmissions of thisdisclosure are often discussed in the context of “uplink transmissions,”aspects of this disclosure are applicable to any transmission from a STAor other wireless device, e.g., direct transmissions, device-to-device(D2D) transmissions, etc. FIG. 3 illustrates a network 300 configuredfor sectorized transmissions. The network 300 includes a base station310 having a serving cell 302, which is divided into a plurality ofsectors 311-313 each of which housing a respective one of the STAs321-323. In embodiments, collisions resulting from the hidden nodeproblem may be avoided in the network 300 by scheduling each of thesectors 311, 312, and 313 to perform transmissions at different times.For instance, the sector 311 may be scheduled for transmission during afirst period, the sector 312 may be scheduled for transmission during asecond period, and the sector 313 may be scheduled for transmissionduring a third period. In some embodiments, scheduling of thetransmissions may be achieved through broadcasting a beacon signal atthe beginning of a respective period. For instance, the base station 310may transmit a first beacon signal to mobile stations in the sector 311to initialize the first period. After expiration of the first period,the base station may transmit a second beacon signal to mobile stationsin the sector 312 to initialize the second period. Following expirationof the second period, the base station may transmit a third beaconsignal to mobile stations in the sector 313 to initialize the thirdperiod. The first beacon may be a beamformed signal directed at spatiallocations within the sector 311, the second beacon may be a beamformedsignal directed at spatial locations within the sector 312, and thethird beacon may be a beamformed signal directed at spatial locationswithin the sector 313.

FIG. 4 illustrates a method 400 for scheduling transmissions, as mightbe performed by a base station. The method 400 begins at step 410, wherethe base station schedules a first sector for transmissions during afirst period. Thereafter, the method 400 proceeds to step 420, where thebase station transmits a beacon to STAs located in the first sector atthe beginning of the first period. Next, the method 400 proceeds to step430, where the base station schedules the next sector for transmissionduring next period. Subsequently, the method 400 proceeds to step 440,where the base station transmits a beacon to STAs in the next sector atthe beginning of the next period. Next, the method 400 proceeds to step450, where it is determined whether additional sectors need to bescheduled. If so, the method 400 reverts back to step 430, where thenext sector is scheduled for transmission. Otherwise, the method 400reverts back to step 410, where the first sector is once againscheduled.

FIG. 5 illustrates a method 500 for performing transmissions, as mightbe performed by a STA. The method 500 begins at step 510, where the STAdetects a beacon signal at a beginning of a period. Next the method 500proceeds to step 520, where the STA performs transmission during theperiod. In embodiments, the STA may perform transmissions in accordancewith CSMA/CA.

In some examples, the beacon may include a scheduling indicator that isselectively directed a certain group of STAs within a sector. Forinstance, the beacon's scheduling indicator may specify a group number,traffic type, traffic class, or some other characteristic associatedwith the group of STAs. In one embodiment, the beacon may schedule STAshaving high SNRs (e.g., cell-center STA) without scheduling STAs havinglow SNRs (e.g., cell-edge STAs) by encoding the scheduling indicator ata rate that is decodable only by STAs having an SNR exceeding a certainlevel or threshold. FIG. 6 illustrates a network 600 configured forsectorized transmissions. The network 600 includes a base station 610having a serving cell 602, which is divided into a plurality of sectors611-613 housing a plurality of STAs 622, 623, and 633. Notably, thesector 612 houses a STA 622 positioned near the center of the cell 602,and a cell 632 positioned near the edge of the cell 602. Due to theirrelative positions to the base station 610, the STA 622 may have ahigher SNR than the STA 632. In some implementations, it may bedesirable to schedule the STA 622 without scheduling the STA 632. Insuch a case, the base station 610 may transmit a beacon comprising ascheduling indicator that is encoded at a coding rate such that thescheduling indicator is decodable by the STA 622, but not by the STA632.

In some embodiments, the scheduling of STAs is performed in accordancewith a channel quality criteria. For instance, scheduling may beperformed in accordance with a received signal strength indication(RSSI) or a signal to interference ratio (SINR) of a beacon signal. Inone embodiment, the beacon contains an information element thatspecifies schedules for STAs having various levels and/or ranges ofchannel quality, e.g., RSSI, SINR, or otherwise. For instance, an AP mayschedule STAs having different signal strengths or signal qualities todifferent time intervals. As an example, an AP may schedule STAs havingchannel quality that is less than a threshold to a first time interval,while scheduling STAs having channel quality equal to or exceeding thethreshold to a second time interval. Indeed, the AP may schedule basedon ranges of channel quality such that STAs having a channel qualitywithin a certain range (e.g., first range, second range, third range,etc.) are scheduled to transmit during a respective interval. In someembodiments, STAs having a channel quality that exceeds a threshold maybe permitted to transmit during any interval, while STAs having lowerchannel qualities may be limited to certain intervals. Schedulinginformation (e.g., time intervals, channel quality thesholds/ranges,etc.) may be specified in the beacon, during association, in a proberesponse during discovery. Additionally, at least some of the schedulinginformation may be a priori information. In accordance with the abovediscussed aspects of this disclosure, different stations located atdifferent distances can be scheduled for different durations, which mayachieve improved fairness and/or network performance (e.g., fewer hiddennode collisions). Scheduling in accordance with channel quality may becombined with other scheduling strategies. For instance, scheduling maybe performed in accordance with channel quality as well as anothercriteria (e.g., sector location, group number, traffic type, devicetype, etc.) to achieve diverse scheduling arrangements. In anembodiment, a receiving STA measures a signal strength received in asignal (e.g., beacon or otherwise), and then compares the signalstrength value with the channel quality thresholds (e.g., indicated bythe beacon, or otherwise) to determine which time interval to transmit,receive, sleep, etc. In the current IEEE 802.11 standards, channelaccess is based on a CSMA/CA method, where each station listens to thechannel prior to transmission.

However, when stations (STAs) are located in different areas and are outof the carrier sensing range of each other, e.g., STA1 and STA2 in FIG.7 cannot hear each other, and thus are likely to transmit to the accesspoint (AP) at the same time, which causes collisions. This is generallyknown as the hidden node problem. Collisions due to the hidden nodeproblem will result in packet losses and retransmissions, which degradethe channel utilization and the quality of service (QoS) of users. In anIEEE 802.11ah network where sensors use very low power to transmit overa long distance, it is expected that hidden node problem could be moresevere as the low transmission power and high path loss make it moredifficult for STAs to detect the ongoing transmissions of sensors.Mitigating the hidden node problem generally should improve theperformance of an 802.11ah network.

One way to reduce collisions among bursty channel accesses of a largenumber of users is to group STAs and allow different groups of STAs toaccess the channel during different time periods. There are differentways to group users. For example, user grouping can be based on the MACaddress of users, or based on the types of applications or QoSrequirements of users. Grouping is helpful to reduce the number ofcontending STAs, and thus is efficient to improve the network resourceutilization. However, such grouping approaches are not specificallydesigned to mitigate the hidden node problem.

For an IEEE 802.11ah network that consists of both high power offloadingSTAs and low power sensors/smart meters, it is recognized that low powersensors are more likely hidden from other STAs and failed incontentions. One way to alleviate the unfair channel access between highpower users and low power sensors is to divide STAs into two groups withdifferent power levels. And high power and low power STAs should contendin different time periods. This approach can eliminate the collisionsbetween high power STAs and low power STAs. However, contentions betweenhigh power STAs and between low power STAs still exist, and low powersensors suffer from hidden node problem as before. In addition, it iscritical to determine the time periods reserved for high/low power STAs,especially when the number of offloading STAs may change over time. Aninappropriate setting of time periods generally will degrade the networkperformance.

An embodiment uses sectorized channel access to alleviate the hiddennode problem in 802.11 networks. Embodiments may be applied to Wi-Finetworks and devices, such as Wi-Fi access points (APs) and Wi-Fistations (STAs).

Sectorization is a method used in cellular systems to reduceinterference. However, in a cellular system the users are allowed toaccess the base station continuously. In contrast, in an embodiment auser can send/receive only during the sector contention duration, whichis signaled in the sector beacon. Further, an embodiment allows sectorsto be dynamically adjusted, rotated in space and in time to minimize thecollisions and interference.

A simple way of efficient sectorized channel access is shown in FIG. 8.The AP first broadcasts a beacon to the STAs in the first sector. Uponreceiving the beacon with the sector information, STAs in the firstsector contend for channel access in the following sector contentionperiod. After that, the AP switches to another sector, and broadcasts abeacon so that STAs in that sector can contend for channel access in thefollowing time period. The AP can switch between sectors in a roundrobin manner or in other deterministic or random sequences. The AP alsocan record the STAs associated in each sector and use this informationfor Traffic Information Map signaling of downlink traffic if needed. Itis also possible that some STAs may hear multiple beacons in differentsectors. In this case, the STAs can select one sector to associate with,e.g., select the sector with a higher received signal strength indicator(RSSI). When a STA observes a decreased RSSI in one sector and decidesto switch to another sector with a higher RSSI, the STA may or may notupdate with the AP. A station may or may not inform the AP about thechange of its sector via management frames. A STA may provide feedbackto the AP with the sector ID. The feedback may indicate received channelquality, e.g., a signal strength of the received beacon. The AP may thenuse the feedback information for various scheduling or other purposes.For instance, the AP may use the feedback information to scheduletransmissions (downlink, uplink, or otherwise), to determine the STAlocation (with various degrees of precision), to schedule direct linkcommunications between two stations in the same sector or betweenstations in different sectors. The feedback information may also be usedto adjust sector size for load balancing or group sizes for loadbalancing. In an embodiment, one or more stations may be allowed totransmit at any time (e.g., by default) irrespective of the sector. Forinstance, stations belonging to a certain group (e.g., group ID 0) maybe permitted to transmit at any time by default, which may allow thosestations to transmit prior to association. The default group of stationsmay be changed during association, which may allow the networkadministrator to restrict transmission by some stations in sectorsreserved for a specific group.

In an embodiment, the association can be implemented as follows. A STAthat comes into the AP coverage is waiting to receive a beacon. Thebeacon carries information about the BSS ID, the sector index, theduration of the sector contention period as well as the period until thenext beacon occurrence. When a STA receives a beacon it can decide toassociate to the AP using that sector index. In the period following thebeacon reception the STA can contend to the channel access as long asthe message does not pass beyond the sector contention duration. In theassociation process the AP respond to a STA in the contention period ofthe same sector. The association ID (AID) allocated to the STA could beselected from a set of AIDs dedicated to that particular sector or froma pool of AIDs called nomadic AIDs, which are dedicated to STAs thatfrequently change their location. The AIDs are used to identify STAs forthe downlink traffic. The AP uses a Traffic Information Map (TIM) tosignal which AID index has traffic in the following sector interval. Ifthe STA is associated with a nomadic AID its information for downlinktraffic could be broadcast in all beacons. In another embodiment, theTIM map is identical in all beacons, i.e. AIDs are not necessarilyassociated with a particular sector. However in an alternativeembodiment a learning algorithm can be used to map AIDs to particularsectors, thus minimizing the TIM size. For instance, after many repliesreceived from a STA in a particular sector that STA can be associatedonly with that sector. Later, if one reply or more replies are notreceived in that particular sector from that particular STA for a pagingmessage, the STA can be paged (via TIM map) in all sectors and declarednomadic. In a different embodiment, a STA can associate itself as fixed(not mobile), which means that the STA will remain for long time in thatsector.

There are several methods for management of the STAs' sector status. Inone method the AP maintains a STA's sector status via association orsector switch procedure, i.e., during the association procedure, the STAand AP negotiate a sector for the STA, and after the association, if theSTA switches to another sector, it performs a sector switch and lets theAP know of the switching. In another method the AP doesn't maintain aSTA's sector status. When a STA wants to get data from the AP, it sendsa message (e.g. PS-poll) to the AP, and the message includes anindicator of the sector. The AP gets the sector indicator and sends datato the STA if there is any data pending for it.

In another embodiment the sector size and duration are variable. A STAis aware about the next period of time it is allowed to transmit orreceive data via the beacon information of sector contention duration aswell as the next beacon occurrence. The AP can dynamically rotate oradjust the size and duration of sectors in order to minimize the hiddennode problem. The TIM map can be broadcast in all beacons. A STA woulddynamically select its own sector based on the RSSI level.

Another embodiment allows the AP to broadcast a beacon to all ormultiple sectors before each contention period. As shown in FIG. 9, theAP can transmit beacons in different sectors in a sequence to informSTAs of the current active sector for channel access. Upon receiving thebeacons, STAs in the active sector contend for channel access while STAsin other sectors can go to sleep until their associated sector becomesactive for channel access. This embodiment generally is more energyefficient for low duty cycle sensors at the cost of more beaconsbroadcast in multiple sectors. To further reduce the beacon overhead,another embodiment is to broadcast beacons in multiple sectors once,followed by contention periods for STAs in different sectors, as shownin FIG. 10. This embodiment generally strikes a tradeoff between theenergy efficiency and overhead reduction.

A different embodiment uses two types of beacons such omni beacons andsector beacons. FIGS. 11-12 illustrate sectorized channel accessincluding an omni beacon. A sector beacon contains the data to access aparticular sector as well as the TIM for fixed stations associated withthat sector and nomadic stations not associated with a fixed sector. Anomni beacon is transmitted periodically after all sectors are parsed.The time division between two omni beacons can contain a sectorized timeinterval when the channel access is done via the sector access method asdescribed above, and non-sectorized access when all the stations cancompete for the channel access irrespective of their location. Anoptional omni beacon can be broadcast to mark the beginning ofnon-sectorized time interval when all the STA could access the channel.

The various embodiments can be combined with other methods of channelaccess as well. For example, the contention period in a single sectorcan be divided between low and high power nodes, etc. In an embodiment,beacons may be transmitted consecutively at designated intervals, e.g.,intervals designated data transmission in various sectors. For instance,transmission of a first beacon for a first sector may be followed bytransmission of a second beacon for a second sector, which may befollowed by transmission of an omni-directional beacon (e.g., for allsectors in the cell). This consecutive sequence of beacons (e.g., firstbeacon, second beacon, omni-directional beacon) may be repeated.

There are several possible methods to implement sectorization. In anIEEE 802.11 network, the access point can employ multiple antennaelements, e.g., a sectorized antenna with fixed beamwidth anddirections, or an adaptive array antenna that can adaptively adjust thebeamwidth towards the desirable directions. Without loss of generality,consider the AP uses a directional antenna and communication with STAswithin its beamwidth; the AP rotates the directions in a sequence tocommunicate with all STAs in the network.

In an embodiment, the sectorized beacon can be identified by a bit or asequence of bits in the PHY preamble (signal (SIG) field) or in the MACheader or in a data payload of the beacon. Another way to identify thesectorized beacon is a particular rotation of the constellation suchquadrature binary phase shift keying (QBPSK).

In another embodiment, when an AP receives an association request or aprobe request it can respond with a probe response that specifies thesector where the sender belongs to. For instance the AP can use anantenna array to identify the direction of the incoming probe request,and then it can reply with a probe response, which contains an index ortype of identification of the sector.

In another embodiment the sector information can be asked by a STA atany time via an explicit message or a message piggy-backed on othermessage. The AP can then either send the sector information via aunicast message to the requester, or collect several requests and sendthe information via a broadcast message that identifies the station andthe sector index the sector belongs to.

More generally, an embodiment allows channel access in a particularspace region at particular time for a particular duration. This methodcan be associated with other sleep/power save schedule methods.

In another embodiment, several APs exchange information about theirscheduling in different space zones such that the interference can beminimized via a distributed or a centralized method.

FIG. 13 is a block diagram of a processing system that may be used forimplementing the devices and methods disclosed herein. Specific devicesmay utilize all of the components shown, or only a subset of thecomponents, and levels of integration may vary from device to device.Furthermore, a device may contain multiple instances of a component,such as multiple processing units, processors, memories, transmitters,receivers, etc. The processing system may comprise a processing unitequipped with one or more input/output devices, such as a speaker,microphone, mouse, touchscreen, keypad, keyboard, printer, display, andthe like. The processing unit may include a central processing unit(CPU), memory, a mass storage device, a video adapter, and an I/Ointerface connected to a bus.

The bus may be one or more of any type of several bus architecturesincluding a memory bus or memory controller, a peripheral bus, videobus, or the like. The CPU may comprise any type of electronic dataprocessor. The memory may comprise any type of system memory such asstatic random access memory (SRAM), dynamic random access memory (DRAM),synchronous DRAM (SDRAM), read-only memory (ROM), a combination thereof,or the like. In an embodiment, the memory may include ROM for use atboot-up, and DRAM for program and data storage for use while executingprograms.

The mass storage device may comprise any type of storage deviceconfigured to store data, programs, and other information and to makethe data, programs, and other information accessible via the bus. Themass storage device may comprise, for example, one or more of a solidstate drive, hard disk drive, a magnetic disk drive, an optical diskdrive, or the like.

The video adapter and the I/O interface provide interfaces to coupleexternal input and output devices to the processing unit. Asillustrated, examples of input and output devices include the displaycoupled to the video adapter and the mouse/keyboard/printer coupled tothe I/O interface. Other devices may be coupled to the processing unit,and additional or fewer interface cards may be utilized. For example, aserial interface card (not shown) may be used to provide a serialinterface for a printer.

The processing unit also includes one or more network interfaces, whichmay comprise wired links, such as an Ethernet cable or the like, and/orwireless links to access nodes or different networks. The networkinterface allows the processing unit to communicate with remote unitsvia the networks. For example, the network interface may providewireless communication via one or more transmitters/transmit antennasand one or more receivers/receive antennas. In an embodiment, theprocessing unit is coupled to a local-area network or a wide-areanetwork for data processing and communications with remote devices, suchas other processing units, the Internet, remote storage facilities, orthe like.

FIG. 14 illustrates a block diagram of an embodiment of a communicationsdevice 1400, which may be equivalent to one or more devices (e.g., UEs,NBs, etc.) discussed above. The communications device 1400 may include aprocessor 1404, a memory 1406, a cellular interface 1410, a supplementalwireless interface 1412, and a supplemental interface 1414, which may(or may not) be arranged as shown in FIG. 14. The processor 1404 may beany component capable of performing computations and/or other processingrelated tasks, and the memory 1406 may be any component capable ofstoring programming and/or instructions for the processor 1404. Thecellular interface 1410 may be any component or collection of componentsthat allows the communications device 1400 to communicate using acellular signal, and may be used to receive and/or transmit informationover a cellular connection of a cellular network. The supplementalwireless interface 1412 may be any component or collection of componentsthat allows the communications device 1400 to communicate via anon-cellular wireless protocol, such as a Wi-Fi or Bluetooth protocol,or a control protocol. The device 1400 may use the cellular interface1410 and/or the supplemental wireless interface 1412 to communicate withany wirelessly enabled component, e.g., a base station, relay, mobiledevice, etc. The supplemental interface 1412 may be any component orcollection of components that allows the communications device 1400 tocommunicate via a supplemental protocol, including wire-line protocols.In embodiments, the supplemental interface 1412 may allow the device1400 to communicate with another component, such as a backhaul networkcomponent.

Institute of Electrical and Electronics Engineers (IEEE) standardspublication 802.11ah is incorporated herein by reference in itsentirety.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

What is claimed is:
 1. A method for sectorized transmissions comprising:scheduling, by a controller, contention-based transmissions for multiplegroups of mobile stations (STAs) in a multi-sector coverage area of aWi-Fi network; allowing one or more STAs belonging to a default group totransmit at any time prior to association; during association,scheduling groups of STAs positioned in different sectors of themulti-sector coverage area to perform contention-based transmissionsduring different time periods such that STAs contend for resources withother STAs in the same sector without contending for resources with STAsin different sectors; and transmitting, by the controller, a firstdirectional beacon signal to a first group of STAs positioned in a firstsector of the multi-sector coverage area, the first directional beaconsignal including control signaling and excluding bearer data, whereinthe first directional beacon signal indicates that the first group ofSTAs is scheduled to perform contention-based transmissions during afirst time period, and wherein the first time period is different from asecond time period during which a second group of STAs positioned in asecond sector of the multi-sector coverage area is scheduled to performcontention-based transmissions, the first directional beacon signalincluding a group identifier (ID) list, wherein STAs associated withnon-zero group IDs that are excluded from the group ID list are notpermitted to perform contention-based transmissions during the firsttime period, and wherein STAs associated with group ID zero arepermitted to perform contention-based transmissions during all timeperiods.
 2. The method of claim 1, wherein the first directional beaconsignal is transmitted at the beginning of the first time period.
 3. Themethod of claim 2, wherein the first directional beacon signal is abeamformed signal directed at spatial locations within the first sector.4. The method of claim 2, further comprising transmitting, by thecontroller, a second directional beacon signal to the second group ofSTAs, the second group of STAs located in a second sector of themulti-sector coverage area, wherein the second directional beacon signalindicates that the second group of STAs is scheduled to performcontention-based transmissions during the second time period.
 5. Themethod of claim 4, wherein the first time period and the second timeperiod do not overlap.
 6. The method of claim 4, wherein the first groupof STAs and the second group of STAs are configured to communicatecontention-based transmissions in accordance with a carrier sensemultiple access with collision avoidance (CSMA/CA) mechanism, andwherein at least some STAs in the first group of STAs are beyond asignal range of some STAs in the second group of STAs.
 7. The method ofclaim 2, wherein the first directional beacon signal schedules a firstsubset of STAs positioned in the first sector to performcontention-based transmissions during the first time period withoutscheduling a second subset of STAs positioned in the first sector toperform contention-based transmissions during the first time period. 8.The method of claim 7, wherein the first directional beacon signalspecifies one or more group numbers corresponding to the first subset ofSTAs without specifying any group numbers corresponding to the secondsubset of STAs.
 9. The method of claim 7, wherein the first directionalbeacon signal specifies one or more traffic types, the one or moretraffic types corresponding to at least some data queued fortransmission by the first subset of STAs.
 10. The method of claim 7,wherein the first directional beacon signal carries a schedulingindicator encoded at a first coding rate, the first coding rate beingdecodable by the first subset of STAs without being decodable by thesecond subset of STAs.
 11. The method of claim 10, wherein STAs in thefirst subset of STAs receive the first directional beacon signal overchannels having sufficient signal to noise (SNR) characteristics fordecoding the scheduling indicator encoded at the first coding rate, andwherein STAs in the second subset of STAs receive the first directionalbeacon signal over channels having insufficient SNR characteristics fordecoding the scheduling indicator encoded at the first coding rate. 12.The method of claim 2, wherein the first directional beacon signalcarries a first scheduling indicator specifying that STAs having areceived signal quality that is within a first range are scheduled toperform contention-based transmissions during a first portion of thefirst time period but not during a second portion of the first timeperiod.
 13. The method of claim 12, wherein the first directional beaconsignal further carries a second scheduling indicator specifying thatSTAs having a received signal quality that is within a second range arescheduled to perform contention-based transmissions during the secondportion of the first time period but not the first portion of the firsttime period.
 14. The method of claim 12, wherein the first directionalbeacon signal further carries a second scheduling indicator specifyingthat STAs having a received signal quality that exceeds a threshold arescheduled to perform contention-based transmissions during both thefirst portion and the second portion of the first time period.
 15. Themethod of claim 1, wherein the Wi-Fi network is a wireless local areanetwork (WLAN) based on a Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 standard.
 16. The method of claim 1, whereinscheduling groups of STAs positioned in different sectors to performcontention-based transmissions during different time periods does notaffect the radiation patterns used to perform the contention-basedtransmissions, and wherein at least one of the contention-basedtransmissions is an omni-directional transmission.
 17. The method ofclaim 1, wherein scheduling groups of STAs positioned in differentsectors to perform contention-based transmissions during different timeperiods does not affect the radiation patterns used to perform thecontention-based transmissions, and wherein at least one of thecontention-based transmissions is a beamformed transmission.
 18. Acontroller comprising: a processor; and a computer readable storagemedium storing programming for execution by the processor, theprogramming including instructions to: schedule contention-basedtransmissions for multiple groups of mobile stations (STAs) in amulti-sector coverage area of a Wi-Fi network; allowing one or more STAsbelonging to a default group to transmit at any time prior toassociation; during association, scheduling groups of STAs positioned indifferent sectors of the multi-sector coverage area to performcontention-based transmissions during different time periods such thatSTAs contend for resources with other STAs in the same sector withoutcontending for resources with STAs in different sectors; and transmit afirst directional beacon signal to a first group of STAs positioned in afirst sector of the multi-sector coverage area, the first directionalbeacon signal including control signaling and excluding bearer data,wherein the first directional beacon signal indicates that the firstgroup of STAs is scheduled to perform contention-based transmissionsduring a first time period, and wherein the first time period isdifferent from a second time period during which a second group of STAspositioned in a second sector of the multi-sector coverage area isscheduled to perform contention-based transmissions, the firstdirectional beacon signal including a group identifier (ID) list,wherein STAs associated with non-zero group IDs that are excluded fromthe group ID list are not permitted to perform contention-basedtransmissions during the first time period, and wherein STAs associatedwith a group ID zero are permitted to perform contention-basedtransmissions during all time periods.
 19. The controller of claim 18,wherein the first directional beacon signal is transmitted at thebeginning of the first time period.
 20. The controller of claim 19,wherein the instructions further include instructions to: transmit asecond directional beacon signal to the second group of STAs in a secondsector of the multi-sector coverage area, the second directional beaconsignal indicating that the second group of STAs is scheduled to performcontention-based transmissions during the second time period.
 21. Thecontroller of claim 19, wherein the first time period and the secondtime period do not overlap.
 22. The controller of claim 19, wherein thefirst directional beacon signal schedules a first subset of STAs locatedin the first sector to perform contention-based transmissions during thefirst time period without scheduling a second subset of STAs located inthe first sector to perform contention-based transmissions during thefirst time period.
 23. The controller of claim 22, wherein the firstdirectional beacon signal carries a scheduling indicator encoded at afirst coding rate, the first coding rate being decodable by the firstsubset of STAs without being decodable by the second subset of STAs. 24.The controller of claim 23, wherein STAs in the first subset of STAsreceive the first directional beacon signal over channels havingsufficient signal to noise (SNR) characteristics for decoding thescheduling indicator encoded at the first coding rate, and wherein STAsin the second subset of STAs receive the first directional beacon signalover channels having insufficient SNR characteristics for decoding thescheduling indicator encoded at the first coding rate.
 25. Thecontroller of claim 18, wherein the Wi-Fi network is a wireless localarea network (WLAN) based on an Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 standard.
 26. The controller of claim 18,wherein scheduling groups of STAs positioned in different sectors toperform contention-based transmissions during different time periodsdoes not affect the radiation patterns used to perform thecontention-based transmissions, and wherein at least one of thecontention-based transmissions is an omni-directional transmission. 27.The controller of claim 18, wherein scheduling groups of STAs positionedin different sectors to perform contention-based transmissions duringdifferent time periods does not affect the radiation patterns used toperform the contention-based transmissions, and wherein at least one ofthe contention-based transmissions is a beamformed transmission.
 28. Amethod for group sectorization to reduce the number of hidden nodes thatsimultaneously access an access point (AP) in a Wi-Fi network, themethod comprising: allowing one or more STAs belonging to a defaultgroup to transmit at any time prior to association; and duringassociation, transmitting, by the AP, sectorized beacons to geographicalareas of a multi-sector coverage area of the Wi-Fi network, thesectorized beacons including control signaling and excluding bearerdata, wherein the sectorized beacons instruct groups of mobile stations(STAs) positioned in different sectors of the multi-sector coverage areato perform contention-based transmissions during different intervalssuch that STAs contend for resources with other STAs in the same sectorwithout contending for resources with STAs in different sectors, each ofthe sectorized beacons including a group identifier (ID) list, whereinSTAs associated with non-zero group IDs that are excluded from a givengroup ID list in a given sectorized beacon are not permitted to performcontention-based transmissions during an interval associated with thegiven sectorized beacon, and wherein STAs associated with a group IDzero are permitted to perform contention-based transmissions during allintervals.
 29. The method of claim 28, wherein the sectorized beaconsinclude a first directional beacon signal and a second directionalbeacon signal, the first directional beacon signal instructing STAs in afirst sector of the multi-sector coverage area to performcontention-based transmissions during a first sector interval, and thesecond directional beacon signal instructing STAs in a second sector ofthe multi-sector coverage area to perform contention-based transmissionsduring a second sector interval.
 30. The method of claim 29, wherein aduration of the first sector interval starts with the first directionalbeacon signal and ends with second directional beacon signal.
 31. Themethod of claim 28, wherein the instructions conveyed by the sectorizedbeacons do not affect radiation patterns used to perform thecontention-based transmissions, and wherein at least one of thecontention-based transmissions is an omni-directional transmission. 32.The method of claim 28, wherein the instructions conveyed by thesectorized beacons do not affect radiation patterns used to perform thecontention-based transmissions, and wherein at least one of thecontention-based transmissions is a beamformed transmission.